CJC-1295 vs. Ipamorelin: GHRH Analog vs. GHRP Comparison

CJC-1295 is a 30-amino acid synthetic analog of growth hormone-releasing hormone (GHRH, residues 1-29) with a C-terminal amidation and four amino acid substitutions designed to improve metabolic stability. The substitutions include D-Ala at position 2 (conferring DPP-4 resistance), Gln at position 8, Ala at position 15, and Leu at position 27. The base peptide sequence (without DAC) is referred to as modified GRF(1-29) or CJC-1295 without DAC, with a molecular weight of approximately 3367.97 Da.

Ipamorelin is a pentapeptide growth hormone secretagogue (GHS) and ghrelin receptor (GHS-R1a) agonist consisting of only 5 amino acid residues: Aib-His-D-2-Nal-D-Phe-Lys-NH2. Its molecular weight is approximately 711.85 Da. The sequence incorporates two unnatural amino acids — alpha-aminoisobutyric acid (Aib) at the N-terminus and D-2-naphthylalanine (D-2-Nal) at position 3 — which distinguish it from natural peptide substrates and confer protease resistance. The C-terminus is amidated.

CJC-1295 with DAC (Drug Affinity Complex) incorporates a maleimidopropionic acid (MPA) reactive linker attached to the Lys residue at position 21. This linker undergoes a spontaneous, irreversible thiol-maleimide conjugation reaction with Cys34 of circulating serum albumin after introduction into plasma. The resulting covalent albumin-peptide conjugate dramatically extends the circulating half-life from approximately 30 minutes (without DAC) to approximately 6-8 days (with DAC) as reported in published pharmacokinetic studies.

The DAC moiety adds approximately 257 Da to the molecular weight, bringing the total for CJC-1295-DAC to approximately 3625 Da. The maleimide group is hydrolytically labile in aqueous solution (ring-opening to the unreactive maleamic acid), which has important implications for reconstitution pH and storage stability. Optimal maleimide reactivity is maintained at pH 6.5-7.0, while hydrolysis accelerates above pH 7.5. This represents a critical quality attribute that differentiates CJC-1295-DAC from the non-DAC variant.

CJC-1295 (without DAC) has the molecular formula C152H252N44O42 with a monoisotopic mass of 3367.90 Da. The peptide contains no cysteine or methionine residues in its modified GRF(1-29) backbone, eliminating oxidative degradation at sulfur-containing sites. Its isoelectric point is approximately 10.1 due to multiple basic residues (Arg, Lys), making it highly positively charged at physiological pH.

Ipamorelin has the molecular formula C38H49N9O5 with a monoisotopic mass of 711.38 Da. The nearly 5-fold difference in molecular weight between CJC-1295 and ipamorelin (3368 vs. 712 Da) represents one of the largest size disparities among commonly studied research peptide pairs. This difference has direct implications for synthesis yield (small peptides are produced at much higher efficiency), purification strategy, and analytical method parameters.

CJC-1295 adopts an amphipathic alpha-helical conformation characteristic of the GHRH peptide family. Circular dichroism (CD) spectroscopy reveals double minima at 208 nm and 222 nm consistent with approximately 60% helical content in membrane-mimetic environments (SDS micelles or trifluoroethanol/water mixtures). This helical structure is essential for receptor binding, as the GHRH receptor recognizes a continuous helical epitope spanning residues 1-29. The D-Ala substitution at position 2 disrupts the local backbone geometry but does not propagate helix destabilization.

Ipamorelin, as a pentapeptide, is too short to form stable secondary structures in solution. Instead, it adopts a compact, turn-like conformation stabilized by intramolecular interactions between the aromatic D-2-Nal and D-Phe side chains. NMR studies suggest the molecule exists as a rapidly interconverting ensemble of conformers in aqueous solution, with the bioactive conformation stabilized upon binding to the GHS-R1a receptor pocket. The unnatural amino acids (Aib, D-2-Nal, D-Phe) restrict the conformational space relative to natural amino acids, pre-organizing the peptide toward its receptor-bound state.

CJC-1295 without DAC is relatively stable as a lyophilized powder, maintaining greater than 95% purity for 24 months at minus 20 degrees C. The primary degradation pathway is deamidation at Gln8 and Asn-containing positions, detectable as late-eluting peaks on RP-HPLC. Reconstitution in bacteriostatic water or sterile water at neutral pH yields solutions stable for 3-4 weeks at 2-8 degrees C.

CJC-1295 with DAC requires more careful handling due to the maleimide moiety. Lyophilized DAC-containing material should be reconstituted in slightly acidic water (pH 6.0-6.5) to preserve maleimide reactivity and minimize hydrolytic ring-opening. Solutions should be used promptly after reconstitution. Accelerated stability studies show that maleimide hydrolysis reaches 50% within 4 hours at pH 7.4 and 37 degrees C, underscoring the importance of pH control.

Ipamorelin exhibits excellent stability owing to its small size, C-terminal amidation, and incorporation of unnatural amino acids that resist common proteolytic cleavage. Lyophilized ipamorelin maintains greater than 98% purity for over 24 months at minus 20 degrees C. Reconstituted solutions at pH 5-7 are stable for 4-6 weeks at 2-8 degrees C. The D-amino acid residues at positions 3 and 4 provide inherent resistance to endopeptidases, contributing to superior solution stability compared to most natural-sequence peptides of comparable size.

RP-HPLC analysis of CJC-1295 (without DAC) is performed on a C18 column (150-250 mm x 4.6 mm, 3.5-5 micrometer) with a gradient of 20-50% acetonitrile in 0.1% TFA over 25 minutes. The peptide elutes as a well-resolved single peak between 16-20 minutes. For CJC-1295 with DAC, the maleimide-containing form and hydrolyzed (ring-opened) form can be resolved chromatographically, providing a functional assay for DAC integrity. UV detection at 214 nm is standard, with 280 nm providing a secondary confirmation wavelength due to Trp and Tyr absorbance.

Ipamorelin analysis requires a shallower gradient (10-40% acetonitrile in 0.1% TFA over 20 minutes) on a C18 column due to its smaller size and moderate hydrophobicity. The D-2-naphthylalanine residue provides strong UV absorbance at both 214 nm and 280 nm, enhancing detection sensitivity. The peptide elutes relatively early (8-12 minutes) under standard conditions. LC-MS identity confirmation is straightforward due to the small molecular weight — the singly charged [M+H]+ ion at m/z 712.4 dominates the ESI mass spectrum with minimal multiply charged species.

Lyophilized CJC-1295 (both variants) should be stored at minus 20 degrees C in a desiccated, light-protected environment. The DAC variant requires particular attention to moisture exclusion, as trace moisture can initiate maleimide hydrolysis even in the solid state. Argon-flushed vials with crimped seals are recommended for long-term storage of DAC-containing material. Reconstituted solutions should be stored at 2-8 degrees C: without-DAC solutions for up to 4 weeks, with-DAC solutions for no more than 48 hours at neutral pH.

Lyophilized ipamorelin is stored at minus 20 degrees C under standard desiccated conditions. Its inherent stability permits short-term storage at 2-8 degrees C for up to one month without significant degradation. Reconstituted ipamorelin solutions are among the most stable peptide preparations commonly used in research, with shelf lives of 4-6 weeks at 2-8 degrees C. Single-use aliquoting is recommended to avoid repeated freeze-thaw cycles, though ipamorelin tolerates 3-5 freeze-thaw cycles with less than 2% purity loss — substantially better than most larger peptides.

DAC (Drug Affinity Complex) is a maleimidopropionic acid linker attached to a lysine residue that enables covalent binding to serum albumin in vivo. This albumin conjugation extends the peptide's half-life from minutes (without DAC) to approximately 6–8 days. CJC-1295 without DAC (also called Mod GRF 1-29) has a much shorter duration of action but sharper pharmacokinetic peaks.

Ipamorelin is only 5 amino acids long (MW ~711 Da), making it significantly easier to synthesize at high purity compared to the 30-residue CJC-1295 (MW ~3367 Da). Shorter peptides have fewer coupling steps and fewer opportunities for deletion sequences or side reactions. HPLC purification of Ipamorelin yields cleaner separations, with research-grade purity routinely exceeding 98%.

Mass spectrometry is the definitive method. CJC-1295 without DAC shows ~3367 Da; with DAC, the MW increases by ~232 Da to ~3599 Da due to the maleimidopropionic acid linker. The HPLC retention time also shifts because the DAC modification increases hydrophobicity. Vendors should provide MS data clearly showing the expected MW for whichever form (DAC or no-DAC) is being sold.

Explore detailed chemical profiles and research guides for compounds discussed in this article:

• CJC-1295: Complete Research Guide → /learn/cjc-1295-no-dac
• Ipamorelin: Complete Research Guide → /learn/ipamorelin

• Read more: Melanotan II vs. PT-141: MSH Analog Structural Comparison → https://www.chemverify.com/learn/melanotan-2-vs-pt-141
• Read more: CJC-1295 (No DAC): Complete Research Guide & Chemical Profile → https://www.chemverify.com/learn/cjc-1295
• Read more: MK-677 vs. Ipamorelin: Oral GHS vs. Injectable GHRP Comparison → https://www.chemverify.com/learn/mk-677-vs-ipamorelin
• Read more: Ipamorelin: Complete Research Guide & Chemical Profile → https://www.chemverify.com/learn/ipamorelin